Producer-gas process



Jan. 14, 1930. Kb s 1,743,717

PRODUCER GAS PROCESS Filed Aug. 31, 192i {M Mil/420W WWI 1 Patented Jan.14,

OFFICE HEINRICH KOPPERS, OF ESSEN-RUHR, GERMANY, ASSIGNOB TO THE KOPPEBSDE- VELOPMENT CORPORATION, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OFPENNSYLVANIA YRODUCER-GAS PROCESS Application filed August 31, 1921,Serial No. 497,372, and in Germany March 14, 1918.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. In,1313) This invention relates to a process for avoiding excessive wear ofthe iron shaft jackets of gas producers or generators operated with lowpressure steam.

For the well known rotary grate gas generators with iron and thereforecooled shafts, it has been understood in the past that in thedouble-walled shaft mantle or jacket the cooling water must not bepermitted to heat above 70 centigrade, so as to preclude the formationof steam under all circumstances.

Temperatures of up to 80 centigrade have been pronounced admissible onlywhen special measures are provided for supervision and immediate actionin case of excesses. Such is the practice in the operating regulation ofthe Kerpely producers or generators. Such generators are exemplified byUnited States Patents 826,036, 1,078,148 and 1,114,072. Instead of thegrate being made polygonal it is commonly made circular but mountedeccentrically.

Now, in connection with gas-generators or producers thus operated inaccordance with such instructions, a peculiar phenomenon appearsinasmuch as the cooling jacket on the inside of the ash-zone wears outwith undue quickness.

The invention is built up on the realization that from the mixture ofair and steam and from the vapors which result in the water pan throughhot ashes, water is precipitated on the inner surface of the metallicwall of gas producers or generators which, in conjunction with thehydrogen sulphide released from the ashes, and the oxygen of the air,causes a violent rusting of the inner part of the stationary shaftsection below the fire zone, this corrosion being helped along stillfurther by the high temperature prevailing there. It must be borne inmind here that in such gas generators it is necessary to introduce largequantities of steam in addition to the low pressure air. By the layer ofashes and slag moving against the shaft wall on the revolving grategasifiers, the rust which forms is always ground off and new innersurfaces thus exposed to the attacks.

According to late theories, the rusting is the ash zone on the innersurface of the cooling jacket forming the shaft walls by means ofsuper-heating of the contents of the cooling jacket, within the limitsbetween which it can be accomplished at all in view of the partlycontradictory requirements. Inasmuch as the surplus heat must bedischarged from the fire zone situated above the ash zone and it isimpossible, in actual practice, to obtain an accurate division betweenthe two zones which, for that matter, also shift around constantly, thissuperheating of the steam coming into contact with the shaft wall mustbe connected with a cooling, by which acontradiction seems to becreated.

The new process is characterized by the fact that instead of thehitherto adopted cooling with cold or re-cooled water, cooling iseffected with highly preheated water, that is to say, water preheated upto close to the boiling limit, by which means the conditionscontradicting each other in the first place are complied with, inasmuchas, on the one hand, the surplus heat from the fire zone proper of thegas producer is discharged with certainty, while a local undercoolingalong the inner surface of the jacket is avoided in the ash-zone whichmight give rise to the condensation of the steam. Let it be recalledhere that the condensing point of steam is not situated at 100 C. herebut, due to the simultaneous presence of air, is below the boilinglimit. Generally speaking, the dew point of the entering air and steammixture is located around 60 0., that is, just around the proximity ofthe present maximum temperature of the cooling water.

Now, in order to avoid, in connection with such cooling by highlypreheated water, the formation of steam, hitherto feared even at allconditions are now adapted to the operation with highly preheated water.Instead of water under pressure, a special cooling liquid of a higherboiling point can also be used. At any rate, in connection with suchfeeding of cooling jackets of gas pro ducers with highly preheated waterunder suitable pressure or a higher boiling liquid,

the desired superheating of the steam coming into contact with the gasproducer in the ash zone is attained without the cooling effect of thefire zone proper being affected thereby.

In order to make the invention more clearly understood the same isillustrated in the accompanying drawing, but not limited to thedetailsshown, which may be varied without departing from the invention.

In said drawing the figure is an elevation of a as producer embodyingthe invention.

Re erring to the drawing, 1 is the shaft of the gas producer providednear the grate with a cooling jacket a portion of which cooling jacketis indicated at 2 by dotted lines. 19 indicates, in outline, an ordinaryrotary ste -grate which is fixed to the ash pan 20. eated water issupplied within this jacket 2 by a pipe 3 descending from a waterreservoir 4 which is suitably suported at a point higher than thecooling acket. The pipe 3 leads from near the bottom of the reservoir tonear the bottom of the jacket, substantially as shown, entering thelatter at 5. In the process of coolin the jacket the water is furtherheated an rises, and enters at 6 a return pipe 7 which enters thereservoir near the top of. the body of water therein. Thus athermosiphon circulation of the cooling (but preheated) body of water ismaintained, from the reservoir to the cooling jacket and from the latterto the reservoir. A certain amount of steam is produced from thecirculating body of water and such steam finds a passage from the jacketto the upper part of the reservoir by means of a steam-pressure reliefvent or pipe 8, and is utilized for (or for a part of) the usual steamsupply to the fuel within the producer. This is accomplished'by a steampipe 9 which leaves the upper part of the reservoir at 10 and deliversbelow the grate 19 at 11 adjacent the customary air supply conduit 21.The steam pipe 8 prevents any steam pressure from obstructing the hotwater circulation. Water is supplied to the reservoir b a pipe 12, andthis is or may be preheated in a heater 13 by excess and waste steamwhich leaves the reservoir by the pipe 14. The described pipes arecontrolled suitably by valves, as indicated, for the water supply pipeat 15, for the downward and upward water-circulation pipes at 16 and 17,and for the steam supply pipe at 18.

In its main features the gas producer is or may be of usual or preferredconstruction, not requiring to be further described. In operation, theproducer when coke fired is preferably operated in the followingwellknown manner. Air from conduit 21 and steam from pipe 9 aresuppliedcontinuously to the usual fuel bed (coke or other fuel) below the grate19 and passed upwardly therethrough. The combustion of the cokegenerates considerable heat, creating an incandescent fire zone in thefuel bed. The carbon dioxide produced by the combustion and water vaporadmitted with the air blast react with the incandescent fuel, giving thecombustible gases, carbon monoxide and hydrogen, diluted with the inertnitrogen of the air. On top of the grate 19 is maintained an ash zone 22comprising a layer of ash about a foot high above the apex of the grate19. This ash zone'is'usually at a sufficiently high temperature toprevent condensation of steam and in fact gives up heat to the air andsteam thereby heating the air and superheating the steam andsimultaneously cooling the ash for discharge. Above the ash zone ismaintained the fire zone 23 varying in thickness with grade and kind offuel used, as, for instance, from two inches with coke breeze to about afoot with stove coke. Above the fire zone isthe coke or distillingzone24 wherein the fuel reaches a height of from three to six feet above thefire zone. Whenlthe air blast encounters the fire zone the oxygencombines with the carbon to carbon dioxide. The oxygen in the air isquickly used up and the carbon dioxide encountering the incandescentfuel is reduced to carbon monoxide. The combustion to carbon monoxidegenerates a great amount of heat, which is partly consumed in reducingcarbon dioxide to carbon monoxide. The remaining heat is dissipated byradiation and absorption by the cooling water in the water jacket andsome of the remaining heat passes out of the producer with thecombustible gas. Were not the steam passed into the fuel bed with theair during manufacture of producer gas, the temperature in the fire zonewould become too hot for commercially successful operation. The ash ofthe fuel fuses and forms clinkers at temperatures uite close to theoperating temperature of t e producer. By

admitting steam along with the air blast,v

control of the temperature resulting from the air blast is readilyeflected. When water vapor encounters incandescent fuel it is reduced tohydrogen and carbon monoxide, the oxygen being taken up by the carbonforming carbon monoxide. This reaction absorbs heat, so thatbyacontrolling ,the amountof steam admitted by the pipe 8, thetemperature of the fire can be regulated. At temperatures below 1160 C.the reaction between carbon and carbon monoxide and water vapor becomesbut partial and is retarded, so that the fire zone is usually maintainedabove said temperature and the ash zone below said temperature but highenough to superheat the steam. The proper'temperature varies accordingto the composition of the ash. A reliable method of controlling theamount of steam admitted is by saturating the air blast to a certaintemperature which for average conditions is about.54 C. This temperaturewill vary with the rate at which the coke is gasified as well as withits composition. The gas leaves the producer through the outlet 25 asshown at the upper part of the producer from which it is passed to otherapparatus to be further treated for removal of dust, etc., or it may bepassed from said outlet directly to the place where it is to be employedfor combustion.

The water jacket 2 extends far enough, as indicated on the drawings, sothat the fire zone will never pass beyond it, and thus prevents sideclinkers which would form on the brick lining of the producer. The steamdrum is so connected as to induce a thermo-' siphon circulation throughthe water jacket 2 and the steam reservoir 4. With the water and steamreservoir 4 located above the top of the water jacket 2 as shown, thewater enters the jacket at about 100 C., and the jacket is operatedunder a pressure of about five pounds per square inch, which preventsany boiling action in the jacket. This corresponds to a temperature of108 C. which prevents any condensation of steam from the blast on thewall of the jacket below the fire zone and opposite the ash zone, whichwould rust the jacket and result in rapid wear, and thereby reduce thegenerating capacity of the producer by reason of the condensation of thegas making steam and the more numerous shut downs of the producer forpurposes of relining the walls thereof. As the water becomes heated itflows upwardly into the reservoir 4 below and near the water levelth'erein where it is relieved of such pressure and flashes into steam.The residual water thence flows back as it cools toward the inlet to thejacket 2.

Thesteam that forms in. the steam space above the top level of the waterspace in the reservoir is conducted by pipe 9, as above described, tothe lower portion of the producer, where it mixes with the air fromconduit 21, and is then passed into the fuel bed to thereby formproducer or other combustible gas. Of course, the steam from thepipe 9of the reservoir also may be used for other purposes than for supplyingthe producer, and steam or the equivalent thereof from other sources maybe employed as an equivalent of the steam from the reservoir 4, therebyreleasing all steam from reservoir 4 for other uses.

What is claimed is- 1. A process of making producer gas in a gasproducer having a metallic water jacket and a water and steam reservoirlocated entirely thereabove and having a lower water space and anuppersteam space, and also having a gas producing chamber having a fuelgasifying zone and an ash zone, which comprises: circulating water fromthe lower portion of the water space of the reservoir downwardly intothe bottom of the water jacket and passing thereinto at a temperature ofabout 100 C. and then upwardly through the top into the water reservoirnear and below the top level of the water therein by thermosiphoncirculation of thewater induced'by the surplus gas making heat absorbedthereby but under suiflcient pressure so that steam formation takesplace substantially only in the reservoir; passing steam from the steamspace of the reservoir to the lower portion of the gas producer, mixingwith air, passing the -mixed steam and air into and through the ash zoneof the gas producing chamber and then into the fuel gasifying zone andthereby forming producer gas; the ash zone and the fuel gasifying zonebeing enclosed by the water jacket and the ash zone having asufliciently high temper.- ature to prevent condensation of steam uponthe inside surface of the water jacket.

2. A method of making gas from a fuel bed in a gas producer having a gasproducing chamber having a fuel gaslfying zone and-anash zone, and alsohaving a metallic water acket enclosing the fuel gasifying zone and theash zone, and a water and steam reservoir located entirely above the andthereb cool the ash, and then into and through t e fuel gasifying zonethereby forming combustible as with said air and said steam; water-cooing the walls of said fuel gasifying zone andsaid ash zone down to atemperature sufiiciently high to prevent condensation of the gas makingsteam u on the inside surface of the water jacket acjacent the ash zoneand to discharge surplus heat from outer portions of the fuel gasifyingzone adjacent said jacket; effecting such water cooling by thermosiphoncirculation of water, induced b surplus gas making heat absorbedthereby, rom the lower portlon of the water space of said reservoirdownwardly into the bottom of the water jacket and passing thereinto ata temperature of about 100 (3., and then upwardly through the top there-5 of and into the water reservoir near and below the top level of thewater therein, and under the pressure of the water in the Water space ofsaid reservoir so that the boilin point of water in said jacket is above100 and that substantial steam formation takes place only in thereservoir and is removed from the circulating water into saidsteamspace.

3. A method as claimed in claim 2 and in which cool feed water admittedto the circulating system is supplied to the system in 'advance of theinflow into the water jacket and is regulated so that such feed watermay mix with and be heated'by the hot inflow stream of water and beprevented from locally chilling the water jacket circulation.

4. A method as claimed in claim 2 and which includes the further step ofventing steam, that may form in the stream of water flowing upwardlyfrom the water jacket into the water'space, from the circulating body ofwater. HEINRICH KOPPERS.

